Automatic defrosting device



Oct. 15, 1963 w. s. TUFTS 3,107,281

AUTOMATIC DEFROSTING DEVICE Filed Jan. 16, 1961 s Sheets-Sheet 1 av sINVENTOR WILLIAM S. TUFTS ATTORN Oct. 15, 1963 w, s u Ts 3,107,281

AUTOMATIC DEFROSTING DEVICE Filed Jan. 16, 1961 3 Sheets-Sheet 2 I0 Fig.2 a- INVENTOR WILLIAM S. TUFTS BY @tWd ATTORNEY Oct. 15, 1963 Filed Jan.16, 1961 W. S. TUFTS AUTOMATIC DEFROSTING DEVICE 5 Sheets-Sheet 3 WILLIAINVENTOR M S. TUFTS ATTORNEY United States Patent 3,167,281 AUTGMATEDEFROSTENG DEVECE William S. Tufts, Columbus, Ohio, assignor to RanceIncorporated, Columbus, @hio, a corporation of Ohio Filed .lan. 16,1961, Ser. No. 823% 6 Claims. (Cl. 2tltl-38) The present inventionrelates to cam operated switching devices, and more specifically to animproved switching device particularly suited for periodicallyinitiating defrosting cycles in the cooling unit of a refrigerator, andfor terminating such cycles in response to the attainment of a givendefrosting temperature in the cooling unit or, after the lapse of apredetermined period of time if the termination is not effected by theattainment of the defrosting temperature.

It is one object of this invention to provide a cam operated switchmeans including a plurality of switch members which are operatedsequentially between two control positions by the rotation of first andsecond cams, respectively, for initiating and terminating defrost cyclesin a refrigerator, for example, the first cam being rotated by a drivingmeans such as a timing device, and the second cam being drivinglyconnected with the driving means by a lost motion connecting meansincluding resiliently yieldable means, the second cam being held againstrotation by a restraining means which releases the cam for movement tooperate the switch members to the sec ond control position in responseto a given condition, such as the attainment of a defrosting temperaturein a refrigerator.

Another object of this invention is the provisions of a cam operatedswitch means of the above mentioned character wherein the restrainingmeans comprises a latch member, preferably formed of bimetal, whichengages a shoulder in the surface of the second cam, and the means forcausing the latch member to release the cam com prises an electricallyenergized element, preferably a resistance type heater, which isenergized to heat the bimetal latch member to release the cam inresponse to an increase in temperature in the cooling unit to apredetermined defrosting temperature, and the first cam having surfacethereon for engaging the latch member and cans ing it to release thesecond cam if the latter has not been released within a predeterminedtime after the defrost cycle is started.

As another object, this invention aims to provide a wholly electricallyoperated control device which is reliable and compact and is free oftubing for thermostatic bellows, external mechanic-a1 motiontransmitting linkages, and the like, and so is adapted to be disposed inany convenient location in a refrigerator housing to which wires may beled.

Other objects and advantages of the invention will be apparent from thefollowing description of a preferred form thereof and from theaccompanying sheets of drawing forming a part of this specification andin which:

FIG. 1 is a schematic illustration of a switching device embodying theinvention and shown connected in the control circuit of an electricmotor driven refrigeration systern equipped with an electric solenoidoperated valve for directing hot gas through the evaporator so as toeffect defrosting thereof;

FIG. 2 is a plan view of the device of FIG. 1, showing certain partsthereof in different positions;

FIG. 3 is a sectional view of the device taken substantially along line3-3 of FIG. 2; and

FIG. 4 is a view similar to FIG. 2 but showing the parts in stilldifferent positions.

Although the control device of the present invention is susceptible ofother forms of construction and is adapted ice to other uses, it will bedescribed hereinafter with reference to the controlling of periodicdefrosting cycles of a refrigerator. Referring now to the drawings,there is illustrated therein a control device, generally indicated atiii, embodying the present invention and shown in FIG. 1 in associationwith the electrical circuit of a refrigeration system which may becontrolled thereby.

The refrigeration system may be of the class having a refrigerantcompressor which is operated by an electric motor M, and an evaporatoror cooling unit, not shown, from which accumulations of frostperiodically require removal. The energization of motor M is preferablycontrolled by a food compartment thermostat T of any well knownconstruction, but which is here shown as being of the 'bimetal type.

The control device 10 comprises a box-like housing '11 which ispreferably molded from a suitable insulating material, such as Bakeliteor other plastic, and which serves to house a cam operated switch meansfor controlling the defrost cycles of the refrigerator. The switch meanscomprises a group of flexible electrical switch members in the form ofspring leaves or blades 12, 13 and 14- mounted within the housing 11.Blade 12 has a contact 12a at one end thereof and has its other endsecured to the rear wall 11b of housing 11 by means of a terminal lug12b which extends through an opening in the rear wall and is fixedtherein by staking. Blade 13 has, near one end thereof, a double contact13a in registration with contact 12a, and is secured at its other end tohousing 11 by a terminal lug 13b extending through an opening in housingwall 11b. Blade 14 is likewise provided at one end thereof with acontact 14:: in registration with contact 13a and is secured at itsother end to housing 11 by a terminal lug 14b extendirn through anopening in housing wall 11b.

Switch members of blades 12 and 14 are held in spaced relation by aspacer member 16 which is retained therebetween by reduced end portions16b and 160 projecting through openings in blades 12 and 14-respectively. Spacer member 16 extends freely through an opening inblade 13, which blade may be referred to as an intermediate switchmember, so that relative movement is permitted between the latter andthe spaced blades 12 and 14 to open and close the contacts thereof.

Rotary, coaxial cam means, comprising a first cam 18 and a second cam19, are provided for effecting the movement of the switch members, orblades 12, 13 and 14 to cause contact 13a to alternatively be inengagement with contacts 12a and 14a so as to make and break certainlater described electric circuits therethrough for controlling thedefrosting cycles of the refrigerator. *Cam 1-8, the periphery of whichis adapted to be engaged by blade 12, is secured to a shaft 21 forrotation therewith. Shaft 21 has a reduced end portion 21a journaled inan opening lie in housing wall 11b, and is connected through suitablereduction gearing, not shown, for rotation by an electric timer motor 22at a rate which may be in the order of one revolution per day, althoughany other suitable rate may be utilized. Timer motor 22 is energizedthrough conductors 23, 24 connecting the motor between lines L1 and L2which supply suitable electric power, such as volts, A.-C., to therefrigerator.

Cam 19, the periphery of which is adapted to be engaged by intermediateswitch member 13 for controlling movement thereof, is mounted on anenlarged portion 21b or shaft 21 for rotation relative to cam 18 andrelative to a flange 210 on the shaft. An arcuate slot 19a is defined incam 19 and flange 210 is provided with a tab 21d which is in engagementwith slot 1% and serves as a lost motion connection to limit therelative rotation between cams i9 and 18. An extension spring 25 is toengage shoulder 19 a. gaged, spring 25 yields to permit rotation of cam18.

connected at one end to a lug 21a of flange 21c and has its other endconnected to a lug 191) formed in cam 19. Spring 25 is led around a drumportion 21 of shaft 21 and serves to yieldab'ly connect cam 19 to thedrive means for rotation with cam 18.

its other end with a hook portion 2611 which is adapted When shoulder19a is so en- An electrically energized resistance type heater 27 isdisposed adjacent latch member 26 and is secured to housing 11 byterminal lugs 27b, 27c fixed in openings in housing wall 11b, and servesto heat bimetal latch member 26 for actuation thereof to release cam 19for rotation by spring 2 5 in a manner which will become ap parent asthe description proceeds.

The surface of cam 19, which is adapted to be engaged by blade 13,extends from portion 19d thereof around in a counter-clockwise directionas viewed in the drawings, and terminates in a surface 19 adjacent asteep shoulder forming a step between that surface and surface 190 ofthe cam. Cam 18, the surface of which is adapted to be engaged by blade12. for controlling its movement, has a cam surface 18a of the sameradial magnitude as surface 1%, and has a sloping surface 1812 whichrises from surface 18a to a generally circular surface 130 ofsubstantially greater radial magnitude than surface 19d of cam 19.Surface 180 extends in a counterclockwise direction, as viewed in thedrawings, and terminates in a surface portion 18d adjacent an abruptstep or shoulder between that portion and surface 18a.

The rotation of shaft 21 by timer motor 22 during normal operation ofthe refrigerator and prior to initiation of a defrost cycle will causecams 18 and 19 to be 7 rotated in unison, cam 19 being held by spring 25in the position relative to cam 18 which is illustrated in FIG. 1,

until shoulder 19:: of cam 19 engages hook portion 26a of latch member26. During such rotation, it will be ob served that blade 12 is engagedwith surface 18d and contact 12a is held in engagement with contact 13a,while spacer member 16 holds blade 14 with contact 14a thereof spacedfrom contact 13a.

The closed contacts 12a, 13a complete a circuit for the energization ofan electric fan F which serves to circustantially simultaneousdeenergization of fan P, will result in a rise in temperature in thecooling unit for removal of frost therefrom. During this time the cam 18will continue to rotate as shown in FIG. 2.

A thermally actuated switch 40, which may be of any conventionalconstruction but is illustrated herein as of the snap acting bimetaltype, islocated in the refrigerator so as to be responsive to the risein temperature in the cooling unit during the defrosting operation.

When a predetermined temperature for effecting the defrosting isattained in the cooling unit, thermally actuated switch 40 completes acircuit which may be traced from line L1 through switch 46*, conductor41, heater Z7, and conductor 42, to line L2, thereby energizing heater27 to heat bimetal latch member 26. -As latch member 26 is heated, itwill bend to the position illustrated in dot-and-dash lines in FIG. 2.to release cam 19 for rotation with respect to cam 18 under theinfluence of spring 25. Such rotation of cam '19 will permit blade 13 todrop from surface 19f bringing contact 13a once again into engagementwith contact 1201 for reestablishing the energization of the circuitfor. fan F, and simultaneously moving contact 13a awayjfrom contact 14::for termination :of the energization of solenoid S. Thereupon, therefrigeration system resumes its cooling function and, as thetemperature of the cooling unit decreases toward its normal value, thethermally responsive switch 40 opens and terminates the energization ofheater 27. Bimetal latch member 26, therefore, cools and resilientlyengages the surface of cam 18, which it follows until it is re-engagedby the shoulder 19a of cam 19*.

The device of this invention includes a fail-safe feature for theprevention of inordinately high temperatures occurring in the coolingunit and food compartment in the event that, for some reason such asmalfunction of switch rotation into its FIG. 4 position with respect tocam 18 late air in the refrigerator over the evaporator thereof.

This circuit may be traced from line L1 through conductor 51 connected.to terminal 131), contacts 12a and 13a, conductor 32 leading fromterminal 12b, fan F,

and conductor 33 to line L2.

As shaft 21 continues to rotate, latch member 26 will restrain cam 19from further rotation with cam '13, and the continued rotation of thelatter will wind spring 25 about drum portion 2:1 Such continuedrotation of cam 18 will permit blade 12 to drop from surface 18d ,tosurface 18a, whereupon blade 13 will engage cam survalve which isprovided for directing hot refrigerant" through the evaporator of therefrigerator for defrosting thereof. This circuit may be traced fromline L1 through conductor 31', contacts 13a and 14a, conductor and withrespect to the switch members 1 2, '13 and 14. The latter are therebyreturned to their normal positions with contacts 13a, 14a open andcontacts 121;, 13a closed to energize fan F.

From the foregoing detailed description of one embodiment of the presentinvention, it will be appreciated that there has been provided thereby aparticularly reliable and effective cam operated switch device which iswell adapted to the controlling of refrigerator defrosting operationsand which includes a fail-safe feature of operation. It will also beappreciated that the invention achieves the eifectivecontrol of aplurality of circuits through the use of cams having limited rotationrelative to one another, whichrelative rotation is controlled by a latchmechanism which is operable in one manner under normal conditions and inanother manner under abnormal conditions.

Although this invention has been described with reference to specificforms of switch devices and specific uses thereof, it is understood thatthe invention isnot limited thereto, but rather the invention includesall those modifications, adaptations, and uses as are reasonablyembraced by the scope of the claims hereof. 7

Having described my invention, I claim:

1. Control apparatus comprising a pair of spaced contact'members, anintermediate contact memberl disposed 7 between said pair of contactmembers, said pair of contact members and said intermediate contactmember being movable relative to one another to alternatively make Inthe event of such a failure,

contact members to control movement thereof, a second rotatable camengageable by said intermediate contact member to control movementthereof, means for rotating said first cam in one direction of rotationwith respect to said contact members, resilient means between said camsfor yieldably urging said second cam to rotate in said one directionwith said first cam, restraining means for releasably holding saidsecond cam against rotation by said resilient means, rotation of saidfirst cam when said second cam is so restrained being effective to movesaid one of said pair of contact members out of engagement with saidintermediate contact member and to move the other of said pair ofcontact members into engagement with said intermediate contact member,and electrically energized means for operating said restraining means torelease said second cam for rotation with respect to said first carn,said second cam thereby being effective to move said intermediatecontact member out of engagement with said other pair of contact membersand into engagement with said one of said pair of contact members.

2. Control apparatus as defined in claim 1, wherein said restrainingmeans comprises a birnetal latch member, and said electrically energizedmeans comprises a resistance type heater adjacent said latch member.

3. Control apparatus as defined in claim 1, wherein said first camincludes means for engaging and operating said restraining means torelease said second cam for said rotation with respect to said firstcam.

4. Control apparatus comprising a plurality of contact members movablerelative to one another to provide first and second operative positionsfor controlling current flow, a first rotatable cam engageable by one ofsaid contact members to control movement thereof, a second rotatable camengageable by another of said contact members to control movementthereof, drive means for rotating said first cam in one direction ofrotation with respect to said contact members, resilient means betweensaid cams for yieldably urging said second cam to rotate in said onedirection with said first cam, restraining means for releasably holdingsaid second cam against rotation by said resilient means, rotation ofsaid first cam when said second cam is so restrained being effective tomove said one contact member to provide said first operative position ofsaid members, and actuating means for operating said restraining meansto release said second cam for rotation with respect to said first camby said resilient means, said second cam thereby being eifective to movesaid other contact member to provide said second operative position.

5. Control apparatus as defined in claim 4, wherein said first camincludes means for engaging and operating said restraining means torelease said second cam for said rotation with respect to said firstcam.

6. Control apparatus comprising a plurality of contact members movablerelative to one another to provide first and second operative positionsfor controlling current flow, first and second rotatable cams coaxiallyarranged in side by side relation and adapted to have relative rotation,said first cam being engageable by one of said contact members tocontrol movement thereof, said second cam being engageable by another ofsaid contact members to control movement thereof, drive means forrotating said first cam in one direction of rotation with respect tosaid contact members, resilient means between said cams for yieldablyurging said second cam to rotate in said one direction with said firstcam, said second cam having a shoulder thereon, a movable latch memberfor engaging said shoulder to hold said second cam against rotation bysaid resilient means, said first cam moving said one contact member tosaid first operative position of said members after a predeterminedangular movement relative to said second cam, actuating means for movingsaid latch member from engagement with said shoulder to release saidsecond cam for rotation with respect to said first cam by said resilientmeans, said second cam thereby being effective to move said othercontact member to provide said second operative position, and said firstcam comprising a rise thereon for engaging and moving said latch memberfrom said shoulder upon angular rotation of said first cam relative tosaid second cam beyond said predetermined angular movement in the eventsaid actuating means fails to operate said latch to release said secondcam.

References Cited in the file of this patent UNITED STATES PATENTS1,935,371 Osborne et a1 Nov. 14, 1933 2,562,481 Swayze July 31, 19512,690,526 Morrison Sept. 28, 1954 2,815,411 Schwarzenbach et a1 Dec. 3,1957 2,970,454 Everhard et a1. Feb. 7, 1961 2,975,612 Everhard Mar. 21,1961 2,979,580 Timm et al. Apr. 11, 1961

4. CONTROL APPARATUS COMPRISING A PLURALITY OF CONTACT MEMBERS MOVABLERELATIVE TO ONE ANOTHER TO PROVIDE FIRST AND SECOND OPERATIVE POSITIONSFOR CONTROLLING CURRENT FLOW, A FIRST ROTATABLE CAM ENGAGEABLE BY ONE OFSAID CONTACT MEMBERS TO CONTROL MOVEMENT THEREOF, A SECOND ROTATABLE CAMENGAGEABLE BY ANOTHER OF SAID CONTACT MEMBERS TO CONTROL MOVEMENTTHEREOF, DRIVE MEANS FOR ROTATING SAID FIRST CAM IN ONE DIRECTION OFROTATION WITH RESPECT TO SAID CONTACT MEMBERS, RESILIENT MEANS BETWEENSAID CAMS FOR UIELDABLY URGING SAID SECOND CAM TO ROTATE IN SAID ONEDIRECTION WITH SAID FIRST CAM, RESTRAINING MEANS FOR RELEASABLE HOLDINGSAID SECOND CAM AGAINST ROTATION BY SAID RESILIENT MEANS, ROTATION OFSAID FIRST CAM WHEN SAID SECOND CAM IS SO RESTRAINED BEING EFFECTIVE TOMOVE SAID ONE CONTACT MEMBER TO PROVIDE SAID FIRST OPERATIVE POSITION OFSAID MEMBERS, AND ACTUATING MEANS FOR OPERATING SAID RESTRAINING MEANSTO RELEASE SAID SECOND CAM FOR ROTATION WITH RESPECT TO SAID FIRST CAMBY SAID RESILIENT MEANS, SAID SECOND CAM THEREBY BEING EFFECTIVE TO MOVESAID OTHER CONTACT MEMBER TO PROVIDED SAID SECOND OPERATIVE POSITION.